Re: [PATCH v2 00/18] Improve PCI memory mapping API

From: Damien Le Moal <dlemoal@kernel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: "Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Kishon Vijay Abraham I" <kishon@kernel.org>,
	"Shawn Lin" <shawn.lin@rock-chips.com>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Heiko Stuebner" <heiko@sntech.de>,
	linux-pci@vger.kernel.org, "Rob Herring" <robh@kernel.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	devicetree@vger.kernel.org, linux-rockchip@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	"Rick Wertenbroek" <rick.wertenbroek@gmail.com>,
	"Wilfred Mallawa" <wilfred.mallawa@wdc.com>,
	"Niklas Cassel" <cassel@kernel.org>
Subject: Re: [PATCH v2 00/18] Improve PCI memory mapping API
Date: Wed, 3 Apr 2024 16:58:42 +0900	[thread overview]
Message-ID: <2cdc7045-e277-4d1f-ad7c-66e4ac819a41@kernel.org> (raw)
In-Reply-To: <20240403075034.GF25309@thinkpad>

On 4/3/24 16:50, Manivannan Sadhasivam wrote:
> On Sat, Mar 30, 2024 at 01:19:10PM +0900, Damien Le Moal wrote:
>> This series introduces the new functions pci_epc_map_align(),
>> pci_epc_mem_map() and pci_epc_mem_unmap() to improve handling of the
>> PCI address mapping alignment constraints of endpoint controllers in a
>> controller independent manner.
>>
>> The issue fixed is that the fixed alignment defined by the "align" field
>> of struct pci_epc_features assumes that the alignment of the endpoint
>> memory used to map a RC PCI address range is independent of the PCI
>> address being mapped. But that is not the case for the rk3399 SoC
>> controller: in endpoint mode, this controller uses the lower bits of the
>> local endpoint memory address as the lower bits for the PCI addresses
>> for data transfers. That is, when mapping local memory, one must take
>> into account the number of bits of the RC PCI address that change from
>> the start address of the mapping.
>>
>> To fix this, the new endpoint controller method .map_align is introduced
>> and called from pci_epc_map_align(). This method is optional and for
>> controllers that do not define it, the mapping information returned
>> is based of the fixed alignment constraint as defined by the align
>> feature.
>>
>> The functions pci_epc_mem_map() is a helper function which obtains
>> mapping information, allocates endpoint controller memory according to
>> the mapping size obtained and maps the memory. pci_epc_mem_map() unmaps
>> and frees the endpoint memory.
>>
>> This series is organized as follows:
>>  - Patch 1 tidy up the epc core code
>>  - Patch 2 and 3 introduce the new map_align endpoint controller method
>>    and related epc functions.
>>  - Patch 4 to 6 modify the test endpoint driver to use these new
>>    functions and improve the code of this driver.
> 
> While posting the next version, please split the endpoint patches into a
> separate series. It helps in code review and can be applied separately.

Which patches ? They are all endpoint related:
 (1) Core code
 (2) test function driver
 (3) rockchip rk3399 controller

(2) and (3) depend on the patches in (1), so splitting the series is a big
possible only if (1) is applied first, so that is a source of delays and breaks
the context of the patches...

-- 
Damien Le Moal
Western Digital Research

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